Permissive Cross-domain Policy with Untrusted Domains Affecting github.com/googleapis/mcp-toolbox/internal/server package, versions <1.2.0
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-GOLANG-GITHUBCOMGOOGLEAPISMCPTOOLBOXINTERNALSERVER-17809924
- published3 Jul 2026
- disclosed28 May 2026
- creditUnknown
Introduced: 28 May 2026
CVE-2026-9739 Â (opens in a new tab)How to fix?
Upgrade github.com/googleapis/mcp-toolbox/internal/server to version 1.2.0 or higher.
Overview
Affected versions of this package are vulnerable to Permissive Cross-domain Policy with Untrusted Domains in the SSE initialization handler due to the use of a hardcoded Access-Control-Allow-Origin: * header. An attacker can gain unauthorized access to sensitive resources by exploiting DNS rebinding techniques when users connect via SSE under specification v2024-11-05.